Neuroprotective effect of ceftriaxone on the penumbra in a rat venous ischemia model

• Ceftriaxone (CTX), a β-lactam antibiotic, increases glutamate transporter-1, GLT-1.
• Neuroprotection by CTX in a model of venous ischemia in rats.
• Dihydrokainate, a GLT-1 blocker, abolished CTX neuroprotection.
• No effect of CTX on spontaneous cortical spreading depression (CSD).
• CTX did not influence expression of NMDA, AMPA and GABA receptors.

ObjectiveGlutamate transporter-1 (GLT-1) maintains low concentrations of extracellular glutamate by removing glutamate from the extracellular space. It is controversial, however, whether upregulation of GLT-1 is neuroprotective under all ischemic/hypoxic conditions. Recently, a neuroprotective effect of preconditioning with a β-lactam antibiotic ceftriaxone (CTX) that increases expression of GLT-1 has been reported in animal models of focal ischemia. On the other hand, it is said that CTX does not play a neuroprotective role in an in vitro study. Thus, we examined the effect of CTX on ischemic injury in a rat model of two-vein occlusion (2VO). This model mimics venous ischemia during, e.g. tumor surgery, a clinical situation that is best suitable for pretreatment with CTX.MethodsCTX (100 mg/kg, 200 mg/kg per day) or vehicle (0.9% NaCl) was intraperitoneally injected into Wistar rats for 5 days before venous ischemia (n = 57). Then, animals were prepared for occlusion of two adjacent cortical veins (2VO) by photothrombosis with rose bengal that was followed by KCl-induced cortical spreading depression (CSD). Infarct volume was evaluated with hematoxylin and eosin (H&E) staining 2 days after venous occlusion. [3H]MK-801, [3H]AMPA and [3H]Muscimol ligand binding were examined autoradiographically in additional two groups without 2VO (n = 5/group). Animals were injected either with NaCl (vehicle) or CTX 200 mg/kg for 5 days in order to evaluate whether NMDA, AMPA and GABAA ligand binding densities were affected.ResultsCTX pretreatment reduced infarct volume compared to vehicle pretreatment (p < 0.05). The effect of CTX pretreatment was attenuated by administration of the GLT-1 inhibitor, dihydrokainate (DHK) 30 min before 2VO. CTX had no effect on the number of spontaneous spreading depressions after 2VO. Analysis of quantitative receptor autoradiography showed no statistically significant difference between rats after administration with CTX compared to control rats.ConclusionsPretreatment with CTX has neuroprotective potential without effect on NMDA, AMPA and GABAA receptor density and spontaneous spreading depression. This effect can be abolished by GLT-1 inhibition, indicating that upregulation of GLT-1 is an important mechanism for neuroprotective action in penumbra-like conditions, e.g. if neurosurgeons plan to occlude cerebral veins during tumor surgery.